The exact moment when Los Angeles Clippers all-star forward Blake Griffin suffered the knee injury that derailed his quest for an Olympic gold medal remained unknown early Friday morning, but a collision with Wizards point guard John Wall possibly contributed to his exit from the team.

Griffin was forced to leave Team USA on Thursday and return to Los Angeles after experiencing discomfort and swelling in the same left knee that limited him during the postseason. The day before, he had signed a five-year, $95-million contract extension with the Clippers and later appeared to aggravate the injury while practicing against the Select Team.

A video of Wednesday’s practice showed Wall attempting to split a double team from James Harden and Griffin. Wall blew past Harden, then his right foot stepped on Griffin’s left foot, causing Griffin’s left knee to twist and buckle awkwardly. Wall lost his balance and stumbled but continued to keep driving toward the basket. Griffin needed help from Harden to get back up.

Moments later in practice, Griffin attempted to elevate for a two-handed dunk but came up lame. He immediately leaned over and grabbed his left knee when he landed. A trainer was later seen placing Griffin’s knee in a brace.

“If we don’t have him, that’s a big loss,” U.S. Coach Mike Krzyzewski said of Griffin after Team USA thrashed the Dominican Republic, 113-59. “Blake was playing really well. He said he did something in the playoffs and whatever he did here probably tweaked what happened there.”

Griffin’s injury has opened the door for Wall’s fellow Kentucky alum Anthony Davis to make the Olympic team as a replacement. Davis traveled with Team USA to Washington, where the team will train for two days and then host Brazil in an exhibition at Verizon Center. Kentucky Coach John Calipari, who coached the Dominican Republic, expects the experience to help Davis become more of a valuable commodity for the New Orleans Hornets.

“This is an unbelievable opportunity,” Calipari said. “The opportunity to be on this team is going to put him ahead in this game about two or three years. To be around true professionals who win. He’s going to be about two years ahead, three years ahead. Coach K did a great job with Derrick Rose. You see he comes back and has an MVP year, and I think the same can happen for Anthony.”

Griffin, who beat out Wall for Rookie of the Year in 2011, was one of just two players on the Olympic team without any international experience, but he is a two-time all-star and made second-team All-NBA last season. His injury is the latest for a team that has also had Chauncey Billups, LaMarcus Aldridge, Dwight Howard, Dwyane Wade and Chris Bosh withdraw because of physical ailments.

“He’s a hard worker. He’s one of the best young players in the league and you don’t want anyone to be injured,” LeBron James said of Griffin. “You can get hurt doing anything. You can get hurt in the summer time just working out as well. I know it [stinks] for him. I just wish him a fast and speedy.”